Flight indicator



' May 19, 1942. c. CRANE 2 283 190 FLIGHT INDICATOR Filed May 18, 1940 4 Sheets-Sheet l /A/l E/V TOR 614,64 G AA/E May 19, 1942. c. J CRANE I 2,283,190

FLIGHT INDICATOR Filed May 18, 1940 4 Sheets-Sheet 2 64,4 4 CZQA/VE May 19, 1942. c. J CRANE 2,283,190

FLIGHT INDICATOR Filed May 18, 1940 4 Sheets-Sheet 3 F1 5. i v F2 5;. 5.

//v vs 7-02 OA'EL L/ 6/QA/VE GENE/j May 19, 1942. Q J CRANE 2,283,190

FLIGHT INDICATOR Filed May 18, 1940 4 Sheets-Sheet 4 Patented May 19, 1942 UNITED STATES PATENT OFFI CE' FLIGHT INDICATOR Carl J. Crane, Dayton, Ohio Application May 18, 1940, Serial No. 335,955

(Granted under the act of March 3, 1883, as amended April 30, 1928,; .370 0. G. 757) 7 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon. i

' This invention relates to aircraftinstruments,

and more particularly to a flight indicator, for

visually indicating the pitch, turn, and bank of an aircraft in flight, and is designed to be an aid in facilitating the proper control and flight of an aircraft by blind or .instrument flying.

The present invention is an improvement over the devices disclosed in United States Patents No. 2,053,182:anc1 No. 2,053,183, granted to myself and to William C. Ocker, relating to blind flying instruments, in which an artificial field of view is provided, simulating the normal visual reference of the ground, sky, and horizon and comprising a colored screen in the form of an endless belt which is moved relative to an indicator representing the aircraft, in response to turning of the aircraft. The horizontal is simulated by a horizontal bar movable relative to'the screen and the indicator, in response to the climbing or descending attitude of. the aircraft. The indicator is operated so as to tilt relative to the horizon to indicate bank of the aircraft and controlled by a gyroscopic device in accordance with the bank of the aircraft. The above-described patented devices satisfactorily serve as an artificial reference and to a great extent eliminate the vertigo experienced by all pilots attempting to coordinate their sense impressions with the indications given by ordinary flight instruments used in blind flying, due to the absence of any external reference with which the pilot may orientate 'the aircraft. I

The above-described patented devices, however, have the disadvantage that the mechanism required to actuate the indicator elements amounts to a duplication of other instruments already on the aircraft, and hence the weight of the flight indicators becomes excessive, and further, the

index, or indicating element, requires movement- .transmitting mechanism in front of the moving screen, thus partially distracting attention'from the moving screen, which primarily is responsible for relieving the vertigo due to turns, by giving the pilot a correct stimulus in turning.

Due to space limitations on present aircraft instrument boards, the size of a flight indicator is accordingly limited, which in turn determines the size of the visual screen; and the problem of .keeping the ratio of the area of the screen to the. area of the index indicator and obstructions as large as possible, becomes serious.

' A solution to the above problem and the principal object of the invention is attained by the provision, in combination with the moving screen or a means to create the optical illusion of motion thereof, of a means to actuate the indicator,

or index, by means placed in the rear, of the screen, and thus for any particular size of screen,

achieving a maximum value of the above-noted ratio. This novel concept is, so far as I am aware, not present in any of the known prior art space provided between two adjacent rollers for passage of the index-operating shaft therethrough, the shaft being capable of rotation as well as vertical displacement.

The invention further has for its object the .provision, in a flight indicator of the character described, of a stationary screen and an optical means to create the illusion of motion of the screen in response to turning of the aircraft. This arrangement also permits actuation of the index element by elements behind the screen.

The invention further has for its object a novel means for transmitting motion from existing aircraft instruments to the flight indicator by photoelectric means, thus not imposing load on the primary instrument so as to in any way affect its indication. a

Other objects and features of novelty not specifically enumerated above will become apparent by reference to the following specification and drawings, in which:

Fig. 1 is a front elevation of one form of flight indicator according to the invention;

Fig. 2 is a view, partly in section, taken on line 2-2 of Fig. 1;

Fig. 3 is a view, partly in section, taken on line 33 of Fig. 2;

Fig.4 is an isometric view to an enlarged scale I Fig. 7 is a modified form of screen for use with a device of the type of Fig. 1;

Fig. 8 is a view, partly in section, illustrating a modified form of flight indicator employing optical means to cause the illusion of motion of the reference screen;

Fig. 9 is a plan view of the arrangement some of the details of the device of Fig. 8;

Fig. 10 is a plan viewof a translucent screen taken on line I0|0 of Fig. 8; and

Fig. 11 is an elevation of a translucent screen taken on line ll-H of Fig. 8.

Referring now to Figs. 1 to 4 inclusive, the reference numeral I indicates the instrument casing, which is provided at one end with a cover glass 2, through which a small index ele ment 4, in the form of a thin piece of metal shaped to have the pictorial outline of an airplane, is observable. The index 4 is mounted on the outer end of a very small-diametered shaft 5, and the index 4 may be tilted by the shaft 5 into an attitude indicative of the bank of an aircraft. The index 4 and its actuating lus received when making a turn in an airplane and using the sky, ground, and horizon as an external reference.

As seen in Figs. 2, 3, and 4, the shaft 5 of the index 4 is rotatably mounted in a pair of arms 6 which are arranged in the form of a fork and formed as a partof a guide block 1, which has tongues 8, which extend into the grooves 9 of the spacedvertical guides I0, so that the guide block is reciprocable in a vertical plane similar to the familiar engine crosshead. The vertical guides ID are secured at each end to the transverse supporting members II, which are suitably secured at their ends to lugs formed in the instrument casing. An l. .-shaped rack member l2 extends'from the guide block 1 and has rackteeth 13 cut in the edge thereof, which mesh with a pinion gear l4 mounted on the end of a shaft l5, which is actuated by one of the receiver units Ilia. of a tandem type Autosyn or Selsyn electrical-motion-transmission receiver or motor [6 mounted in the instrument casing I. Rotation of the shaft IS in either direction will cause the gear l4 to move the rack l2 and the block I up or down in the guides l0. thus moving the shaft 5 and theairplane index 4 in a vertical plane, as indicated by the arrows in Fig. 4.

A hollow shaft ll, which surrounds and is concentric with the shaft l5, is actuated by a second receiver unit 16b of the tandem receiver l6, and a spiral tooth gear'l8 is mounted on the outer end of the hollow shaft l1 and may be actuated in either direction of rotation by the shaft ll. Th gear [8 meshes with a corresponding spiral tooth gear l9 arranged to rotate in a plane at right angles to the plane of rotation of gear H3. The gear I9 is secured to the upper end of a vertical splined shaft 20, which has a plurality of splines 2| arranged parallel to the longitudinal axis of the shaft and formed on the exterior surface of the shaft. The splined shaft 20 is splined bore 26 (see Fig. 4) which cooperates with the splines 2! on the vertical shaft 20, so that the gear 25 is freely slidable along the shaft but nonrotatable with respect thereto. The gear 25, being carried by the guide block I, is reciprocable therewith. The spiral-tooth gear 25 meshes with a corresponding spiral-tooth gear 21 arranged to rotate in a plane at right angles to the plane of rotation of gear 25 and mounted on the inner end of the index-actuating shaft 5. The supporting bearing arms 6 of the index shaft 5 straddle one of the vertical guides l0 and serve to maintain the index shaft 5 freely rotatable and perpendicular to the plane of the vertical guides l0 and the guide block I. The gears 25 and 21 are always in mesh and movable in a vertical plane with the guide block 1 without causing rotation of the index shaft 5.

Rotation of the hollow shaft I! in either direction by the receiver unit l6b of the tandem Autosyn receiver l6 causes gear l8 to rotate gear l9 and splined shaft 20 a proportional amount in either direction .of rotation of shaft 20. Rotation of the splined shaft 20 in either direction will cause a corresponding rotation of the gear 25, which in turn will correspondingly rotate the gear 21 and the index shaft 5 through an angular amount proportional to or equal to the angular deviation of the shaft l1 and in a direction determined by the arrangement of the spiral-toothed gearing, which is determined such that the airplane index 4 rotates in the same direction as the airplane on which the instrument is mounted, viewed from the pilots cockpit looking forward; and the outline of the airplane index 4, as seen in Fig. 1, is representative of a view of an airplane looking forward from the tail.

As seen in Fig. l, the airplane index 4 is located in front of a reference screen assembly, generally indicated by the reference numeral 30, the-construction of which will now be described. The screen 30 is formed by a plurality of small parallel vertical rollers 3| arranged so that they are nearly in contact at their adjacent edges, with the exception that a space 32 is left between the center pair of rollers sufllcient for the small index-actuating shaft 5 to project therethrough and to be capable of vertical displacement without contacting the rollers. The rollers are'painted with a narrow black stripe at their central portions, with a narrow stripe of luminous paint on either side of the black stripe, and the black stripe and the black and 'luminous stripes on the rollers are aligned to nately painted blue'and white, while below the horizon line 33 the rollers are painted in a, color to resemble the earth, or painted a dull black, or painted alternately black and white. The space on the rollers above the horizon line furnishes a background representing the sky as viewed from the airplane, while the space below the horizon furnishes a background representing the earth's surface, and the horizon line represents the horizon, or line of meeting of earth.and sky, as seen, from an aircraft and universally used as an external reference in determining the flight attitude of aircraft-under conditions of good visibility.

As seen=in Figs. 2 and 3, the rollers 3| have reduced-diameter shoulder portions 34 at each end, which are pivotally mounted in suitable bearings in the transverse members H, and at Y their lower ends each-roller is provided with a the vertical supports 31 and 38. As seen in Fig. 3, the worm 36 has a spindle portion 39 at its outer end, which extends beyond the vertical support 38 and has a spiral-tooth gear 48 mounted on the end thereof which may mesh with a spiral-tooth gear 4|, mounted on a shaft 42,

which is rotatably and slidably supported at one end by bearing boss 43, carried by the transverse wall-3 of the instrument casing and supported at its other end by a manually rotatable and axially slidable sleeve 44, which has a spiraltooth resetting gear secured thereto and rotatable therewith. The sleeve 44 extends through the front wall of the instrument casing I, and is capable of being rotated and moved axially by the knob 46. A spur gear 48 is mounted on the shaft 42 in axial spaced relation to the gear 4| and is contacted by a compression spring 49, loosely rotatably mounted on the bearing boss 43. The spring 49 serves to maintain the gears 40 and 4| normally in mesh, but by pushing in the knob 46 the sleeve 44 engages, the side of gear 4| and moves the gear and its shaft 42 axially to the left, demeshing gears 40 and 4| and meshing the gear 40 with the resetting gear 45, so that by rotation of the knob 46, the worm 36 and rollers 3| may be manually rotated in either direction to perform a resetting operation hereinafter described. The spur gear 48 on shaft 42 meshes with an idler gear 58 pivotally mounted on the vertical support 38, and the idler gear 58, in turn, meshes with a spur gear 5| secured on the end of a shaft 53 and rotatable therewith. The shaft 53 forms the rotor shaft of a third Autosyn receiver 54, which, in rotating in either direction, will cause worm 36 and rollers 3| to rotate a proportional amount. The resetting operation above described causes spur gear 48 onlshaft 42 to be demeshed from idler gear 50 and thus from driving connection with the receiver 54.

The Autosyn motor, or receiver 54, is adapted to be electrically connected to a corresponding transmitter unit (not shown), which is adapted to be connected to a directional gyro device, preferably the unit provided in the well-known gyro-controlled automatic pilot. The receiver unit 54 is thus positionally controlled and rotates through an angle equal to or proportional to the azimuth change in heading of the airthe rollers rotate in a direction opposite to the direction of the aircraft turn. Adjacent the upper ends of each of the end rollers 3| a semicircular guide 55 is provided to serve as a guide for a narrow endless belt 51 made of flexible material and containing azimuth indicia on its outer surface. The belt .51 passes over the rollers 3|, and one of the end rollers is provided with sprocket teeth 58 which engage perforations in the belt 51 and serve to drive the belt; and in addition certain other of the rollers 3| are roughened or serrated at their upper ends, so as to assist in driving the belt 51 and take up slack. The belt 51 and the azimuth indicia thereon pass across the front face of the instrument and are visible through the cover glass 2, as clearly seen in Fig. 1. Since the rollers 3| are rotated by the Autosyn receiver 54 and connected gearing, an amount proportional to the degree of turn of the aircraft, the belt 51, or azimuth scale, serves to indicate the degree of angular change in azimuth heading of the aircraft. The' azimuth scale, or belt 51, is set .to a desired initial setting by means of the resetting knob 46.

As above described, it is seen that the rotation of the shaft |5 of the Autosyn receiver |6a of the tandem receiver unit "l6, caused the I airplane index 4 and its associated shaft 5 to be vertically displaced up or down, depending on the direction of rotation of the shaft |5. The Autosyn receiver unit |6a is adapted to be electrically connected to a corresponding Autosyn transmitter (not shown), which, is connected to a horizontal gyro device (not shown), preferably such as employed in the well-known automatic pilot and responsive to changes in pitch of the aircraft-4. e., the climbing or diving attitude of the aircraft with respect to a horizontal plane. The gearing between'the Autosyn receiver unit |6a and the guide block rack I2 is such that for a movement of the aircraft into a climbing attitude, the guide block 1, index shaft 5, and index 4 will move up to a position above the horizon line 33 on the screen 30 to indicate the magnitude ofthe angle of climb. If the aircraft assumes a diving attitude, the index 4 will accordingly be moved below the horizon line 33 on the screen 30, to properly indicate a diving condition.

The index 4, as above described, is rotatable by the shaft 5 in response to the angular deviation of the shaft H, which is the rotor shaft of the Autosyn receiver unit |3b of the tandem type Autosyn unit IS. The receiver unit |6b is electrically connected to a corresponding Autosyn transmitter unit (not shown), which is controlled preferably by the horizontal gyro unit of an "automatic pilot" in response to banking of the aircraft about its longitudinal axis. The shaft 5 then rotates throughan angle equal to or proportional to the degree of bank of the airplane, and the miniature airplane index 4 assumes a tilted position relative to the horizon line 33 of the screen 30, indicative of the directionand degree of bank of the aircraft.

Operation In the above-identified Crane and Ocker patents, the concept of causing a reference screen to have a motion of translation relative to the,

.ment past the airplane index 4, and the direction of rotation of the rollers is arranged such that if theairplane makes a right-hand, or clockwise, turn, the rollers 3| will revolve clockwise and will give the illusion that the background is moving to the left, as seen in Fig. '1; and for a left-hand turn, the direction of rotation of the rollers 3| will be reversed and the background will appear to move to the right, as seen in Fig. 1. The above operation of the rollers and the background createdthereby serve to give an artificial reference which gives thecorrect visual stimulus of the turning of the aircraft, while the azimuth scale gives the change of the azimuth heading in the turn.

When the aircraft makes a correct banked turn to the right and maintains the level flight position, the miniature airplane index 4, as seen in Fig. 1, will tilt in a clockwise direction to indicate the degree of bank; and the shaft 5 will be in the plane of the horizon index line 33 on the rollers 3|. The rollers will rotate so as to give the illusion of the movement of the background aircraft will cause the counter mechanism to inindicate the angles from zero to three hundred sixty degrees. Fig. 6 illustrates the arrangement of the counter dials of Fig. 5 so as to be visible through the instrument cover glass.

Fig. 7 illustrates a modified form of screen for use in the device of Figs. 1 .to 4 inclusive, in which the rollers 3| are replaced by a pair of large rollers 3|a and a pair of small rollers 3lb. The rollers 3|a. are spaced the length of the desired background, while the rollers 3| b are centrally disposed, with a small clearance space 32 therebetween, through which the index-actuating shaft 5 may pass. An endless belt 65, made of flexible material, passes over each adjacent pair of rollers 3|a and 3|b. The pair of screens 65 form an unbroken background, except for the vertical slot, or opening, 32. Each of the rollers 3|a is provided with spiral-tooth pinion gears 35, which mesh with the respective worm sections 36a, similar to rollers 3| of the device of to the left. If the airplane is in a climbingi attitude, the miniature airplane index 4 will be above the horizon; and if a turn is made to the right, the index will bank or tilt in a clockwise direction to indicate that a climbing turn to the right is being made. If the attitude of the aircraft is such that it is descending, the index 4 will move below the horizon line 33; and if a right turn is made, the index 4 will indicate a right-hand diving turn. A similar operation takes place for turns to the left, except that the direction of motion of background appears to move to the right, as above described. The de-' vice indicates the true flight attitude during straight flight-i. e., whether the aircraft is flying level, climbing, or descending.

The fact that all of the operating mechanism for causing indicating movement of the miniature airplane index 4 is placed behind the screen assembly 30, makes possible a. maximum ratio of the area of the screen to the area of the index and other obstructions, which ratio governs the value of any such instrument in serving as an artificial reference which will relieve the vertigo caused in making turns when flying without the use of external flight references, and in increasing the value of the instrument in visually integrating the sum of the separate indications now given by individual instruments.

Figs. 5 and 6 illustrate a modified form of azimuth-indicating means to replace the endless belt azimuth indicator 51 of the device of Figs. 1 to 4, inclusive. As seen in Fig. 5, the upperreduced-shouldered portion 34 of one of the rollers 3|. is extended through the upper transverse supporting member H', and is suitably slotted, as at 60, to engage the lower end of a shaft 62 to form the well-known screwdriver, type of drive. The shaft 52 drives a conventional counter device 53 having three counterwheels and adapted to indicate all angles in degrees from zero to three hundred sixty degrees. The driving ratio between the roller 3|, which drives the counter,

mechanism and the counter gear train is such that a three hundred sixty degree turn of the Figs. 1 to 4. The worm sections 36a are rotated by the spiral-tooth gear 40 in the same manner as worm 35 (Fig. 1) is actuated. Each of the rollers 3Ia is provided with sprocket teeth 65, which engage the perforations 61 in the respective belts 65 and serve to positively drive the belts. The belts 55 are each'provided with central horizon index lines 33, and the space above the horizon line is painted to imitate sky scenery, while the space below the horizon-line is painted to resemble the earth, in the same manner as in the above-noted Crane and Ocker patents. The screen assembly is employed with the remaining structure illustrated in Figs. 1 to 4 inclusive and operates in a similar manner, in that the screens 65 of Fig. Tcause an illusion of translatory movement of the reference background as a whole. The screen assembly of Fig. '7 permits the actuation of the .miniature airplane index 4 in the same manner as the same is actuated in the device of Figs. 1 to 4 inclusive.

Figs.'8 to 11 inclusive illustrate a form of the invention in which an opticalmeans is employed to create the illusion of a translatory movement of the reference screen relative to the miniature airplane index. As seen in Fig. 8, the instrument comprises a casing III of rectangular shape closed by a removable cover glass structure 12 and having a partitioned chamber I4 at its rear end, forming a housing for a directional gyro of conventional design and generally indicated by the reference numeral 15. The gyro unit 15 comprises an air turbine type gyro wheel 15 rotatably mounted by means of shaft 11 in the gymbal frame 18, which is pivotally mounted by means of pivots I9 for rotation about a longitudinal axis in the vertical gymbal frame 80. The vertical gymbal frame is pivotally mounted for rotation about a vertical axis by means of a lower pivot extension 8|, carried by a ball type bearing 82, formed in the end of a boss 83, which extends from the instrument casing. The upper end of the frame 80 is provided with a spindle 84, which is rotatably mounted in ball bearing 85. Air at atmospheric pressure enters the nozzle by means of the passage'SI; and the conduit 92 is connected to a means, such as a vacuum pump or Venturi tube (not shown), which serves to exhaust the chamber 14 and create a pressure difference between the inlet passage 9| and the exhaust conduit 92 sufllcient to cause a high velocity jet of air to impinge on the turbine vanes of the gyro wheel I5, rotating the wheel at a high velocity. The gyro wheel 15 when set in motion tends to remain fixed in space in the vertical plane in which it was initially set in motion, and any turning of the aircraft-about the axis 8I84 causes the casing I to revolve about the vertical gyro frame 80' or to create relative motion between the gyro wheel and its supporting casing. The gyro is caged and set by conventional manual means actuated by the resetting shaft 94, axially movable and rotatable by the resetting knob 95.

The vertical pivot shaft 84 of the gyro frame 80 extends through the upper wall of the chamber 14 and has a conical-shaped mirror I00 rigidly secured thereto and rotatable therewith. The mirror I00 has small colored pieces of irregular shape, I02, inserted therein and small black numerals I03 are arranged in a band around the mirror and serve as an aximuth scale in a manner hereinafter described. A light projector I04 and a reflecting mirror I05 are each mounted on a bracket I06 secured to the instrument casing. The projector I04 and mirror I05 are arranged in the rear of the conical mirror I00 such that light from the projector will strike the surface of mirror I00 and be reflected into themirror I05, from whence the light is transmitted forward to the ground glass screen I08 supported bythe wall I09 in the forward portion of the instrument casing I0. The mirror I04 is made of a curved shape such that the light received from mirror I00 will be reflected as divergent rays illuminating a considerable area of the ground glass screen I08. The colored glass sections of the mirror will reflect colored light to the screen I08, and the colored spots, or patterns, on the screen I08 will make an illuminated background, with sharply defined shades and shadows due to the variation in ilumination in various parts thereof. The image of the numerals on the mirror I00 will also appear on the ground glass screen. As the aircraft on which the instrument is mounted turns-for example, to the rightthe instrument casing 10 will rotate about the spindle 84 of the gyroscope I5, and light from the projector I03 will impinge on the colored sections of the mirror I00, causing spots or zones of colored light of a lower intensity to appear on the ground glass screen I08; and the spots of light will appear to move from right to left on the screen I08 and create the illusion of movement of the background relative to the miniature airplane index. The small numerals I02 on the mirror I00 will be transmitted in shadow outline to the screen I08 and serve to indicate the actual number of degrees of the turn and the new azimuth heading of the aircraft.

The miniature aircraft index IIO, similar in outline to the airplane index 4 of the device of Fig. 1, is mounted on a horizontal shaft III, rotatably mounted in a bearing II2, carried by the ground glass screen I08. At its inner end, the shaft III has a lever II3 rigidly secured thereto at right angles to the axis of shaft III; and the lever II3 extends downwardly and passes between the forks II5, extending in a plane at right angles to the. plane of a vertical lever H4 and formed as bent-over portions thereof. The lever I I4 is fixed on the end of a shaft II6 andis rotatable therewith, the shaft I I6 being a pointer shaft of a sensitive electric meter Ill, which is connected by electrical connections H8 and H9 to a photoelectric cell I20 of the self-current-gencrating, or Photronic type. The levers I I3 and H4 are carefully counterbalanced to eliminate the effects of acceleration forces thereon.

The Photronic cell I20 is mounted in the easing I22 of a horizontal gryroscope I23-preferably that of the automatic pilotthe gyro wheel being pivotally mounted in gymbal rings I24 and I25, so that the gyro may remain horizontal independent of either pitching or rolling motion of the associated aircraft. A light projector I26 is mounted on a bracket I21, secured to the horizontal gyro casing I22 and arranged to direct a beam of light onto the light-sensitive surface of the Photronic" cell I20, causing the same to generate a current proportional to the intensity of the light transmitted thereto. A translucent screen I30, in the shape of a spherical segment, is carried by the gyro I23 and arranged so that the optical axis of the screen is perpendicular to the horizontal plane of the gyro I23, the screen being located between the light source, or projector I26, and the Photronic cell I20. The translucent screen I30 (see Fig. 10) is made such that the screen gradually becomes more opaque in going from longitudinal zone a to zone 0, the longitudinally extending zones,

however, having a constant density or lighttransmitting character throughout their longif transmitted by the projector I26, by adjustment of the manually controlled rheostat I29, connected in one of the power supply leads I28, for the lamp in the projector I26, and by initially adjusting the fixed resistance of the conductors IIO-I I9, light passing through the translucent screen I30 will cause Photronicfcell I20 to gen erate a current sufiicient to deflect the arm or pointer II4 of the sensitive electric meter III to the mid point of its motion. The arm II3 will then be vertical, and the miniature airplane index IIO will be horizontal. If the aircraft banks or rolls about its longitudinal axisfor example, the right wing drops-then casing I22 will rotate clockwise about the axis of the gyro gymbal ring I25, and the light from projector I26 will pass from the line :c-x (Fig. 10) through a more dense zone, and the intensity of light striking the Photronic cell I20 will decrease, causing a decreased current to flow into meter I I1 and thus permitting the pointer II4 to move counterclockwise toward its zero position, causing arm II3 to rotate-the shaft III and the miniature airplane index H0 in a clockwise direction to indicate that the bank or roll is clockwise or that the right wing is down. Similarly, if the airplane banks to the left-i. e., the-left wing dropsthe light transmitted from the projector I26 to the Photronic cell I20 will pass through a less dense zone of the translucent screen I30 so that a greater intensity of light will fall on the Photronic cell I20, causing a greater current to pass through the meter Ill, in turn causing an increased deflection of the pointer II4, which will cause a counterclockwise rotation of the arm I I3, shaft III, and the miniature airplane index I I0, which will then correctly indicate the banked position of the airplane. Because of the fact that all longitudinal lines along the translucent screen I30 are of constant optical density or light-transmitting character the gyro I23 by means of a vertical translucent shield I32, which is interposed between the projector I26 and a Photronic" cell I34, mounted in a vertical plane in casing I22. The light projector I26 is provided with a second lightdirecting opening and lens, for directing a beam of light onto the light-sensitive cell I34, in a plane at right angles to the plane of the beam transmitted to cell I20.

As seen in Fig. 11, the vertical translucent shield I32 is divided into parallel arcuate zones which are made with a constant light-transmitting density throughout their length and curved so that light passing through the screen will pass through the same zone, irrespective of rotation of the instrument casing I22 about the axis of rotation of gyro gymbal ring I25. The zones are made of a constantly decreasing lighttransmitting character'from the upper zone a to the lower zone Referring again to Fig. 8, when the aircraft is in level flight, light passing through'the'translucent screen I32 will cause the Photronic cell I34 to generate a current proportional to the intensity of the light'passing through the screen. If the aircraft should move into a descending, or diving attitude, the casing I22, light projector I26, and Photronic cell I34 will rotate in a counterclockwise direction about the pivotal axis of the gymbal ring I24,- and light from projector I26 will pass through an optically denser portion over portions I of the pointer arms I40 are painted black with luminous edges, so that 'the bent-over portions serve as a horizon index, similar to the horizon bar in the above-noted Crane and Ocker patents. By inserting a suitable ballast resistance (not shown) in circuit with the Photronic cell I34, the current value may be adjusted so that when the aircraft is in the level flight position, the shaft I39 of the meter' I38 of screen I32, allowing light of a diminished intensity to fall on the cell I34, causing a decreased current to be generated thereby. If the aircraft should move from the level flight position into a climbing attitude, light from the projector I26 will pass through a less dense portion of the screen, and the intensity of the light falling on the Photronic cell I34 will be increased, causing an increased current to be generated thereby. The variation in current from the cell I34 may be thus made to vary in a manner nearly proportional to the aircraft deviation from the level flight position, Where space permits, the vertical shield I32 may be curved in the vertical plane with the center of curvature at the pivotal axis of the gymbal ring I24; and the shield, or screen I32, in such a case, will be an arcuate extension of the translucent shield, or screen I30. For the purposes of the present instrument, however, the shield I32 may be made straight, as-shown, without introducing appreciable errors. The variation in current generated by the Photronic" cell I34 in response to changes in attitude about the pitching axis of the-aircraft, is utilized to actuate a horizon-reference indicator in the following manner:

The Photronic. cell I34 is connected by conductors I35 and I36 to a sensitive electric meter I38 having a double end pointer shaft I39, to each end of which is secured a counterweighted pointer arm I (see Fig. 9). The meter I38 is similar to the meter 1 and is mounted in the instrument casing I0 such that the pointer shaft I39 is transverse of the casing and in, the same horizontal plane as the index-actuating shaft III. As particularly seen in Fig. 9, the pointer arms I40 are made of very thin lightweight ma- .terial, and each pointer arm extends forward to the index-actuating shaft III. The bent.-

will be deflected in a clockwise direction, as seen in Fig. 8, to the mid point of its range, at which time the pointer arms I40 will be horizontal and in the same plane as the index-actuating shaft III. If the aircraft assumes a diving attitude, the cell I34 will generate a diminished current and cause a decrease in the deflection of the shaft I39 of meter I30, causing the pointer arms I40 and the horizon bars I to move up an amount nearly proportional to the deviation of the aircraft and indicate, by the relative positions of the horizon bars I and the miniature airplane index IIO, that the aircraft is in the diving position. Similarly, if the aircraft moves into a climbing attitude, the greater current generated by the cell I38 will cause an increased deflection in a clockwise direction of the shaft I39 and pointer arms I40, causing the horizon bars I4I to move below the miniature airplane index III) and indicate that the aircraft is climbing.

' While the translucent screens I30 and I32 have been described as having zones with varying light-transmitting character, it .is to be understood that these zones may be of infinitesimal width, so that the variation in optical density from one extreme zone to the other will be uniform, though for practical purposes it is preferred to make the translucent shields from narrow strips, each having a different optical density.

Operation rectional gyro unit I5, in combination with the optical transmission, comprising light projector I04, mirrors I00 and I05, and ground glass screen I08, serves to indicate the existence of a turn by creating the optical illusion of a translatory motion of the background furnished by the illuminated ground glass screen I08 past the miniature airplane index IIO ina direction opposite the direction of turn, thus correctly visually simulating the visual stimulus received by the pilot of an aircraft when making a turn using the backgroundof the sky, earth, and horizon as a reference. The indication of the magnitude of the turn is in the manner previously described.

The novel photoelectric method of transmitting indications of the aircrafts change in position to the flight indicator, permits the use of present existing change-in-position-responsive instruments, as transmitting units, without imposing any load on such instruments or devices.

In medium-sized and large aircraft, which are generally equipped with the gyroscopically controlled automatic pilot, the various gyro units thereof may serve as an excellent means for transmitting change in aircraft position indications to the flight indicator. It is to be noted however that the instrument may incorporate all of the various devices necessary for its actuation as units thereof, and a rate-of-climb indicator may obviously be used as a means to control the indication of climb, descent, or level flight attitudes of the aircraft as given by the flight indicator.

While the device illustrated in Figs. 8 to 11, inclusive, employs a reflecting optical system to create the optical illusion of a translatory motion of the reference background screen relative to the airplane index, it is apparent that the mirror I may be replaced by a translucent screen operatively connected to the directional gyroscope l and having a pictorial colored or variable optical density pattern thereon, including opaque azimuth indicia. I 'he translucent screen may be arranged to be interposed between the light projector I26 and the screen I08, and either rotated or given a translatory motion relative to the screen I08 to cause the optical illusion of motion of the-screen I08, as well as to transmit the azimuth indicia thereon, such an arrangement employing the familiar motion picture system of projection.

While preferred forms of the invention have been illustrated, other modifications falling within the scope of the invention as defined by the appended claims, will become apparent to those skilled in the art.

I claim:

1. A flight indicator for aircraft, comprising an instrument casing; a background screen disposed within said casing and comprising at least two sections movable in translation and centrally spaced apart to'form a vertically extending aperture in the screen; a miniature airplane index mounted in front of said screen; a shaft on which said index is mounted, said shaft projecting through the aperture in said screen; means responsive to lateral inclination of an associated in and a horizon index cooperating with said screen; a rotatable shaft extending through said aperture, a miniature airplane index mounted on said shaft, said airplane index'being visible rela tive to said screen and horizon index; slidable means providing a journal bearing for rotatably mounting said shaft, means responsive to pitching movement during flight for actuating said slidable means for causing vertical displacement of said shaft and airplane index above and below said horizon index, driving means for rotating said shaft in either direction irrespective of the movement of said slidable means; and means responsive to lateral inclination during flight for actuating said driving means to cause a rotation of said shaft and tilting of ,said airplane index to indicate aircraft bank; each-of the'means for respectively causing verticaldisplacement and tilting of said airplane index relative to said horizon index being adapted to act severally or simultaneously and being positioned behind said reference screen.

5. The structure as claimed in claim 4, in which said reference screen comprises a plurality of vertically disposed rollers, each having a zone .of contrasting color above and below said horizon index, a pair of said rollers being spaced for the passage of said airplane-index-actuating aircraft operatively connected to said shaft behind said background screen for causing rotation of said shaft and a corresponding tilting of said index indicative 'of the lateral inclination of the associated aircraft; and means responsive to turning of the associated aircraft operatively connected to said screen sections to cause a motion thereof creating an optical illusion of translatory motion of said background screen across the entire field of view relative to said index in a direction opposite the direction of turning of the associated aircraft.

2. The structure as claimed in claim 1, in which said background screen comprises a plurality of parallel vertically disposed rollers, a central pair of said rollers being spaced sufllcient for the passage of said index-actuating shaft therebetween, and -means for simultaneously rotating said rollers about their respective axes actuated by said means responsive to turning of the associated aircraft.

3. The structure as claimed in claim 1, including a horizon reference line and a means located behind said screen and responsive to pitchin inclination of said associated aircraft for causing vertical displacement of said miniature airplane index above or below said horizon reference line indicative of the pitching deviation of said associated aircraft from a horizontal plane.

4. In a flight indicator having a reference screen with a vertically disposed aperture thereshaft 'therebetween, and means responsive. to

turning during flight for simultaneously rotatingv each of said rollers about its longitudinal axis an amount and at a rate proportional to the amount and rate of turning.

6. The structure as claimed in claim '4, in which said reference screen comprises a pair of endless belts, each having one face thereof forming a part of said screen and the adjacent ends of said belts being spaced apart to allow said airplane-index-actuating. shaft'to extend therebetween so as to be capable offree rotary 'movement and vertical displacement; and a means responsive to turning during flight for causing a simultaneous motion of said belts across the field I of view relative tosaid airplane index so 'that the direction of relative motion is to the left for a right turn and vice versa for a turnto the left.

7. A bank and turn indicator for aircraft, comprising a translucent reference screen having an aperture therein, a horizon index cooperating with said screen to divide the view of the same into sections representing the view of-the earth and sky, a rotatable shaft extending through the aperture in said screen, a miniature airplane index mounted on said shaft in front of said screen and tiltably thereby with respect to said horizon line to indicate the lateral inclination during flight, an inclinometer operatively connected to said shaft behind said reference screen to actuate the same, a turn indicator operative to indicate the direction and magnitudaof the change of azimuth during a turn, a source of light for illuminating the screen, a movable means interposed in the path of transmission of light from said light source to said screen operative in any one position to vary the illumination of said screen to form contrasting illuminated zones thereon, and an operative connection between said movable means and said turn indicator whereby said movable means causes a moving light pattern across said screen having a motion in a direction opposite the direction of turning.

cam. J. CRANE. 

